The present embodiments relate to a method for estimating a radiation dose of an X-ray generated by an X-ray source not initially detected penetrating an object under examination.
An X-ray imaging chain may be used in X-ray systems for medical diagnostics of a human body in order to visualize processes within the body. In such cases, the X-ray imaging chain generates X-ray images that serve as a basis for diagnosis. When an X-ray is recorded, an exposure dose is measured and controlled, for example, via a radiation measurement chamber. The radiation measurement chamber may be an Automatic Exposure Control (AEC) chamber. The dose is determined in the form of an analog voltage corresponding to dose power or a digital value over a time integral. The dose is determined in the analog case on the basis of an impulse value generation with simultaneous counting. The dose is determined in the digital case by using a digital automatic exposure control chamber on the basis of an upwardly integrated counter value.
DE 10 2006 037 740 describes an X-ray diagnosis device for creating a series of X-ray images with a high-voltage generator for an X-ray emitter and with an X-ray detector. Disposed in front of the X-ray detector is a dose measurement chamber, to which measurement electronics are connected in a first control circuit that creates an actual AEC signal. An imaging system is connected via a second control circuit. The dose is determined from the image content via a component of the imaging system, and an actual dose signal is subsequently generated. During the recording of a series of X-ray images, the actual AEC signal and the actual dose signal are fed to a combined control electronics, via which the high-voltage generator may be controlled.
A basic characteristic of automatic exposure control chambers is a dose power-dependent time delay that causes the switch off to take place correspondingly later than planned. This time delay is also known as dose lag time or dead time. The dead time ranges between 300 μs and around 1 ms, for example, depending on the dose power. The disadvantage of the X-ray diagnosis device described is that, in the event of very short recording times (e.g., 1-5 ms), errors resulting from the dead time of the automatic exposure control chamber lie in the unacceptable two-digit percentage range, and optimum irradiation of an object to be examined may not be guaranteed.